1. Field of the Invention
The present invention relates to furnaces or heaters, and more particularly to apparatus for measuring the temperature in furnaces or heaters. Even more particularly, the present invention is related to thermocouples used to measure the temperature of furnace or heater tubes, and apparatus for attaching thermocouples to furnace or heater tubes.
2. Description of the Prior Art
Thermocouples are commonly attached to furnace or heater tubes used in industrial applications to monitor the temperature of the surface of the tube to prevent damage to the tube from excessive temperatures. Such heaters or furnaces are well known in the art and are used to heat fluids flowing through the tubes.
Apparatus for attaching such thermocouples to the surface of furnace or heater tubes are known in the art. Exemplary of the related art are the following U.S. Pat. Nos.: 2,048,680; 2,048,681; 2,151,648; 3,143,439; 3,901,080; 3,939,554; 4,854,729; 4,971,452; 5,172,979; 5,382,093; 5,993,061; and 6,334,707.
It is also known in the art to connect thermocouples directly to heated bodies such as furnace or heater tubes by welding, or peening or swaging into a hole drilled in the heated body or fastener such as a clip connected to the heated body. Shields and insulation are then placed over the thermocouple to prevent damage to the thermocouple and are welded to the heated body.
Commonly, removal and replacement of thermocouples requires welding a new thermocouple directly to a furnace tube or to an apparatus connected to a furnace tube. Damage may be done to the tube during removal of the old thermocouple and the welding of the new thermocouple to the furnace tube, and the tube may require removal from the furnace and re-welding to the furnace after the thermocouple is replaced.
In accordance with the present invention there is provided a thermocouple holder assembly for a furnace tube including a heat sink block for welding to the furnace tube, the heat sink block having a first bore therein for slidably receiving the distal end of an elongated sheathed thermocouple, the heat sink block having a hollow heat sink tube extending from the first bore for receiving a portion of the thermocouple, and a heat shield for welding to the furnace tube having walls for shielding and completely enclosing the heat sink block to shield the heat sink block from ambient heat on the exterior of the heat shield, the heat shield having a cavity therein for receipt of the heat sink block and the heat sink tube and flexible insulation material placed over the heat sink block and the heat sink tube, one of the walls having a second bore extending therethrough to the cavity for slidably receiving the thermocouple, the second bore being positioned in the heat shield wall for alignment with the heat sink tube for conveying the thermocouple through the second bore to the heat sink tube, the heat shield having a third bore extending through one of the walls and intersecting the second bore for receipt of a fastener for placement in the third bore for selectively fastening the thermocouple to the heat shield and for selectively releasing the thermocouple from the heat shield.